Chiral materials exhibiting no center of symmetry are isotropic birefringent materials having a "handed" molecular structure. This handedness makes them optically active and capable of rotating a plane of polarized light transmitted through them. Polarizing coatings and filters comprise birefringent materials capable of transforming light into polarized light. Thus, chiral materials may be used as polarizers in the fabrication of polarizing coatings and filters.
Recently, Pelet and Engheta in IEEE Transactions on Antennas and Propagation 38, 90-98 (1990) have suggested the use of optically active materials in guided-wave structures to produce chiral waveguides. A chiral waveguide, also known as a chirowaveguide, comprises a cylindrical waveguide or parallel conducting plates filled with a homogeneous isotropic chiral material. Applications for chiral waveguides include integrated optical devices, telecommunications electronics systems, printed-circuit elements, and optoelectronics devices.
Organic polymers are known to be compatible with semiconductor electronics technology, can withstand high temperatures during processing, and have a large capacity for engineered properties. In addition, poly(aryl)ethers are a unique class of organic polymeric materials. They are characterized by their excellent mechanical strength per unit weight, high thermal stability, and hydrolytic resistance. Thus, they are often referred to as high performance polymers as compared with polyethylene, polystyrene, polymethylmethacrylate, polybutadiene, etc. Commercially available poly(aryl)ethers include polyphenylene oxide (PPO(.RTM.), polyether ether ketone (PEEK(.RTM.), polyether sulfone (UDEL.RTM.), and polyether imide (ULTEM(.RTM.).
Brunelle et al. disclose in U.S. Re. 34,431 cyclic poly(aryl)ether polymers prepared from racemic spirobiindane compounds. These cyclic polyethers include high molecular weight cyclic polyetherimides, polyetherketones, and polyethersulfones, which can then be converted to linear polymers. The cyclic spirobiindane polyetherimides exhibit high glass transition temperatures, typically greater than 200.degree. C. U.S. Pat. No. 5,145,926 to Patel et al. discloses high molecular weight polyetherketones and polyethersulfones containing derivatives of racemic indane compounds. The racemic indane polyethersulfones were found to exhibit a high glass transition temperature of 215.degree. C.
In general, most applications of synthetic polymers require good thermal stability to withstand high temperature processing, but do not require optical activity. However, for use in the formation of polarizing coatings or filters and for utility as chiral waveguides, birefringent materials having polarizing properties must be employed. Due to the low birefringence of the achiral prior art poly(aryl)ether polymers mentioned above, they are not useful in such applications.
Chiral polyether polymers are typically synthesized by polymerizing optically active monomers having an unsaturated alkene adjacent to the ether oxygen in the presence of a catalyst. The unsaturation is usually due to a carbon-carbon double bond in vinyl, acrylic, or methacrylic derivatives. For example, F. Ciardelli discloses in Encyclopedia of Polymer Science and Engineering Optically Active Polymers 10, 463-493 (1987) the preparation of optically active vinyl ethers, alkenyl vinyl ethers, and alkyl vinyl ketones from unsaturated chiral monomers. In addition, Ciradelli discloses the use of chiral cyclic monomers in forming linear optically active polymers through ring-opening polymerization reactions. These chiral polymers have shown utility as chiral reagents and catalysts for asymmetric synthesis, as packing materials for chromatographic columns for enantiomeric resolution, and as chiral materials for the preparation of liquid crystal polymers.
However, the aforementioned optically active polyethers exhibit low glass transition temperatures (&lt;150.degree. C.) and have low thermal stability. Thus, these chiral polymers are not useful in applications that require high temperature processing, such as in the fabrication of optoelectronics devices.
Therefore, a need exists for optically active organic polymers that retain the aforementioned thermal advantages associated with high performance poly(aryl)ether polymers. In addition, a need exists for optically active polymers that can be used as polarizers and that can be used in high temperature processing applications, such as in the fabrication of opteoelectronics devices. Such polymers should have excellent processability and should be tough, durable, thermally stable, and water resistant.
The novel chiral polyether polymers of the present invention meet the above needs. Surprisingly, the present polyethers are not only optically active, but also exhibit excellent hydrolytic resistance and thermal properties, such as high glass transition temperatures or melting points. Thus, unlike known optically active polymers, the present polymers are particularly useful in high temperature processing applications.